In 2005, the EPA issued the Clean Air Mercury Rule to cap and reduce mercury emissions from coal-fired power plants. This rule, combined with the EPA's Clean Air Interstate Rule (CAIR) or other rules, may require significant reduction in mercury emissions from coal-fired power plants in the U.S. as early as 2010.
Significant coal resources exist around the world that have the potential to satisfy much of the world's energy needs for a long period of time. The U.S. has large amounts of low-sulfur coal sources, e.g. Powder River basin coal in Wyoming and Montana, but such sources contain non-negligible amounts of mercury in both the elemental and oxidized forms. Thus, some type of mercury emission mediation technology is necessary in order for coal-fired energy plants to utilize such sources of coal without substantial mercury emissions.
The Department of Energy has presented information from several studies that indicate mercury emissions during combustion of coal fuels can be lowered by treatment of the coal fuel stocks with low levels of bromine.
Brines that are produced in several areas of the world contain substantial quantities of bromide salts, such as sodium bromide. Bromine can be recovered from such brines by treatment with chlorine to oxidize the bromide to bromine. Processes for electrolytic conversion of bromide to bromine are also known; but electrolytic conversion is an expensive alternative to the aforedescribed process. Catalytic oxidation of bromide to bromine by use of oxygen or air mixtures has been reported; but no successful, economic, commercial operation is in place today.
Brominated activated carbon is known for use in reducing mercury emissions from coal-fired power plants. However, production of brominated activated carbon requires the transport and handling of bromine which is corrosive and toxic. It also requires a high degree of on-site technical expertise regarding bromine handling procedures and emergency response actions.
Given the foregoing, it would be commercially beneficial to have new, commercially viable processes for minimizing mercury emissions from coal and other fuel stocks.